This invention relates generally to sockets for electronic device packages.
Electronic devices are operating at faster and faster speeds. With this increase in performance, a designer should take into consideration the possibility of increased noise, cross-talk, ringing, etc. that may occur on the signal lines of the electronic device.
Electronic devices may reside in any of a number of package technologies, for examples, flat pack, dual in-line package (DIP), pin grid array (PGA), and land grid array (LGA). Electronic devices such as microprocessors generally reside on packages with multiple pins such as an LGA.
Current LGA socket technology has inherent I/O performance limitations. Manufacturing capability limitations of LGA socket technology limit minimum socket height, socket self inductance, socket loop inductance, and socket capacitance. These aspects of the socket design impose impedance discontinuities that limit the performance (i.e., speed) of I/O signaling in electronic device products that use present LGA socket technology.
Currently, these problems have been addressed by reducing socket height, controlling pitch, optimizing mold material, and optimizing the land configuration. However, these solutions have limitations. For example, regarding socket height, the height of the socket can only go so small to control inductance. Similarly, land pitch can only control inductance to a certain degree. Moreover, to reduce impedance discontinuities with land configuration, one may have to completely surround a signal land with ground lands. This requires too many lands to practically use a socket for a microprocessor application.
At high frequencies, impedance (Zo) is equal to the square root of inductance divided by capacitance (Zo=(SQRT L)/C). Current solutions attempt to control the impedance by controlling the inductance (L). In current solutions however, the inductance is generally too high, or the inductance to capacitance ratio is not controlled to the degree desired. Therefore, when an electronic device in a LGA package, for example, is plugged into a socket, signals on the lands of the LGA package see impedance discontinuities causing signal integrity problems.
Thus, there is a need for better LGA packages.